Wednesday, March 6, 2013

The 80/20 rule supposes that 80% of your results comes from 20% of the work you did. It has further been argued that the last 20% of a project is the most difficult and important. One can understand how these two ideas tie together and they indeed have some sort of merit. Those last few stages in preparing to bring a product to market/project to close are critical because the details are important. The last post ended with the Beagle Bone Case being at the 80% stage. The design language and major features have been settled. Now is the time to take the case and sort out imperfections, adjustments for changes in new/changed constraints, cost effective production and so forth. Basically, the iteration and revision of a design in the stages prior to being salable.

In this case, additional feature requests were made that changed core parts of the design. Room needed to be added to accommodate an additional shield or board, as well as any wiring. This resulted in the case being expanded 10mm on the sides and increasing the height by 18mm. Time was also taken at this stage to refine existing features. The SD Card port was enlarged for easier access and the press-fit to close system improved alongside adding Greebling to the case top. This version of the Beagle Bone Case was then 3D Printed.

Unfortunately, there is a problem with the case as designed; it takes over 5hrs 30min to complete in addition to suffering from curling due to its new size. Internally, a design that takes longer than 180-225min to 3D print is no longer affordable to offer as a product. The time removes full 3D printing as an option for manufacturing after including the cost of running the 3D Printer and man power.

Highlighting the curling on the edges.

MDF as Case Top in Composite Test

Perhaps the design could be reworked, turning the case into a composite of materials? Doing that would reduce the print time, lowering the plastic used. So, I removed the roof of the case and instead opted to laser cut a top that would glue into place. The idea here being that the roof layers generated by Skeinforge take much longer to complete than the layers for the walls themselves. But while the print time was reduced, it was not reduced enough to justify offering the case as a salable product. That is not to say the Beagle Bone Case would be a poor product, it is just outside our current manufacturing capabilities to offer it as a product made and sold by I Heart Engineering.

Engineering asks that problems not only be solved by building something, but building it in a manner that is practically useful to all involved parties. This lead to the decision that the final version of the 3D Printed Case can still be offered to the community via Thingiverse to do with as they please and a new method of housing the Beagle Bone on the TurtleBot must be created. Another alternative would be to outsource the handling of the 3D Printing to a partner like Shapeways or travelling down the road of injection molding with services likeProtomold. The injection molding route may yield the best results, but it comes with it's own requirements so the case will enter another lengthy design phase. In both situations, crowd sourcing initial interest would be the smartest way to judge whether its a worthwhile endeavor.

To reach this point, over 6 versions of the Beagle Bone Case were created, not including any of the test parts used. The project spanned 10 regular working days. More than 24 hours of actual 3D Printing Time were logged.

Overview of various case part iterations

Where the Project is Now

Testing Inserts Effect on Acrylic

Although the Full 3D Printed Case as a salable product was not achieved, the product idea itself does not die. The plan now is to scale back the design and focus of the simplicity of the intended function. We need a way to mount the Beagle Bone to the TurtleBot. The simplest and most effective way to achieve this is to create an adapter for the Beagle Bone to the TurtleBot. This can be achieved with a formed plate containing mounting points for the Board and TurtleBot. While not as consumer market friendly as the full case, it serves the core functionality, is within our current manufacturing ability, and is useful to our current and future customers.

Fortunately, we already have all the necessary dimensions and constraints on hand due to earlier work. Because this makes creating the adapter a much faster process, there was a realization that we can make this adapter plate universal between several development boards at once. What started as an idea to build cases for boards that had universal mounting points, is now a simple adapter plate that works with the Beagle Bone, Raspberry Pi, and Arduino suite of Boards.